Cyclonic separation apparatus

ABSTRACT

A cyclonic separation apparatus comprising at least two series connected separation stages and a receptacle for collecting material separated by the separation stages is described. The first stage comprises a first cyclone separator, and the second stage comprises a plurality of parallel connected second cyclone separators. The first and second separation stages are connected by at least one transfer duct which extends through the receptacle and transfers fluid that has been partly cleaned by the first separation stage to the second separation stage.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a cyclone separation apparatus.

2. Related Background Art

Cyclonic separation apparatus are well known apparatus for removingparticles from a gas flow without the use of filters. Cyclone separatorshave found utility in the field of vacuum cleaners to separate dirt anddust from the airflow. It is well known that the separation efficiencyof cyclonic separators is dependent upon the force which is applied tothe particles in the airflow, in accordance with the following formula:F=2mv ² /d,where

-   F=the force applied to the particles;-   m=the mass of the particle;-   v=the flow velocity; and,-   d=the diameter of the cyclonic air flow

Thus, it is evident that the separation efficiency is inverselyproportional to the diameter of the cyclone chamber, such that smallerdiameter cyclones are more suited to separating lighter particles thanlarger diameter cyclones. Accordingly, it is well known for vacuumcleaners to incorporate a first upstream separation stage, comprising arelatively large diameter cyclone and a plurality of parallel connecteddownstream cyclones having a smaller diameter. In use, the upstreamcyclone separates coarse dirt and dust from the airflow, whereas thedownstream cyclones separate the finer dirt and dust.

Cyclonic separators for vacuum cleaners comprising two stages ofseparation have been proposed. U.S. Pat. No. 2,171,248 discloses anarrangement whereby a high efficiency downstream cyclone is nestedco-axially inside a low efficiency upstream cyclone. The respectivecyclones discharge their separated solid material into a removablereceptacle comprising a central chamber for the material discharged fromthe downstream cyclonic chamber, and an annular chamber from materialdischarged from the upstream cyclonic chamber.

EP1674021 discloses a two stage cyclonic separator for a vacuum cleanercomprising a low efficiency upstream cyclone separator, followed by anarray of parallel-connected mini cyclones disposed in an annularchamber, which surrounds the first cyclonic chamber. Partly cleaned airthat exits first stage passes upwards by way of an axially orientatedcentral outlet and is fed into the high efficiency cyclones. However,the complex alignment of the flow path between the two stages of theseparation gives rise to a pressure drop.

DE 202006017010 discloses a two stage cyclonic separator for a vacuumcleaner again comprising a low efficiency cyclone separator followed byan array of parallel connected high efficiency cyclone separatorssituated above the first stage. Partly cleaned air leaving the firststage is ducted upwards through an annual cavity between the highefficiency cyclones and the outer wall of the separator unit and is thenducted regularly inwards to the respective high efficiency cyclones.This arrangement gives rise to less of a pressure drop. However, insituations where the high efficiency cyclones are not disposedequidistantly on the periphery of the separator unit, the cyclones canbecome unevenly loaded with respect to the dust laden air, and canresult in the blocking of some cyclones.

SUMMARY OF THE INVENTION

In accordance with the present invention, a cyclonic separationapparatus which alleviates the above-mentioned problem comprises a firstseparation stage and second separation stage,

-   -   the first stage comprising a first cyclone separator, the second        stage comprising a plurality of parallel connected second        cyclone separators, the apparatus further comprising a        receptacle for collecting material separated by the second        cyclone separators,    -   the first and second separation stages arranged in fluid        communication by at least one transfer duct which transfers        fluid that has been partly cleaned by the first separation        stage, to the second separation stage,    -   wherein the at least one transfer duct extends through the        receptacle.

Preferably, the at least one transfer duct extends substantiallyparallel to the rotational axis of the cyclone separators of the firstand second separation stages.

Preferably, the second cyclone separators are arranged in plurality ofgroups.

The cyclonic separation apparatus preferably comprises a plurality oftransfer ducts. Each transfer duct preferably transfers fluid to onegroup of the plurality of groups of second cyclone separators.

Preferably, each group of second cyclone separators are arrangedequidistantly from the downstream end of the respective transfer duct toavoid uneven loading of the second cyclone separators of the group.

Preferably, the receptacle is disposed partly above the first separationstage.

Preferably, the cyclonic separation apparatus comprises a collectionchamber disposed axially within the first separation stage, forcollecting material discharged by the first and second cycloneseparators.

Preferably, the receptacle is funnel shaped and discharges materialseparated by the second separation stage into the collection chamber.

Preferably, the first separation stage and second separation stage areconnected in series.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described by way ofexample only and with reference to the accompanying drawings in which:

FIG. 1 is a longitudinal-sectional view through the separation portionof a 2-stage cyclonic vacuum cleaner in accordance with the presentinvention;

FIG. 2 is a perspective view of the top of the first stage of thecyclonic vacuum cleaner of FIG. 1, when the second stage is removedtherefrom;

FIG. 3 is a perspective view of the bottom of the second stage of thecyclonic vacuum cleaner of FIG. 1;

FIG. 4 is a perspective view of the top of the second stage of thecyclonic vacuum cleaner of FIG. 1, when fitted to the first stage; and

FIG. 5 is a perspective view of the top of the second stage of thecyclonic vacuum cleaner of FIG. 1, when fitted to the first stage andwhen a cover portion is fitted thereto.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1 of the drawings, there is shown the separationportion of an upright vacuum cleaner. The separation portion is mountedto a chassis (not shown) incorporating a handle, the lower end of thechassis being pivotally interconnected to a wheeled floor-cleaning headincorporating a rotatable agitator brush.

The separation portion comprises a generally cylindrical uprighthousing, which houses the first and second separation stages 10, 11 atits lower and upper ends respectively, the second stage 11 being fluidlyconnected downstream of the first stage 10.

The first stage 10 comprises a tubular side wall 12 defining acircular-section cyclone chamber 13. The lower end of the tubular sidewall 12 is provided with a closure 14, which can be opened to allowseparated dirt and dust to be emptied from the chamber 13.

An inlet duct 15 for carrying dirt and dust laden air from the floorcleaning head extends tangentially into the upper end of the tubularside wall 12 of the first stage 10. An elongate tubular container 16extends through the cyclone chamber 13 along the centre axis thereof.The lower end of the container 16 is sealingly closed by a disk 17,which is mounted to the closure 14 such that the lower end of thecontainer 16 is also opened when the closure 14 is opened. The upper endof the container 16 communicates with an outlet of the second stage 11from which the separated fine dust is discharged.

The upper end of the first stage 10 is closed by an annular end wall 18having a central aperture 19, through which the elongate container 16extends. A perforated shroud 20 extends from the end wall 18 into thecyclone chamber 13, the lower end of the shroud being sealed against theexternal surface of the tubular container 16.

Referring also to FIG. 2 of the drawings, a circular manifold 21 issealingly mounted on top of the end wall 18 of the first stage 10. Themanifold 21 comprises six upstanding tubular projections 22, which aredisposed at equally spaced circumferential positions on a concentriccircular line on the manifold 21. The lower end of the projections 22fluidly communicate with the space inside the shroud 20 through theaperture 19 in the end wall 18 of the first stage 10.

Referring to FIG. 3 of the drawings, the second stage 11 comprises acylindrical main body 23, which is fitted to the upper end of the firststage 10, the manifold projections 22 extending into correspondingapertures 24 which extend through the body 23 between opposite sidesthereof. Each aperture 24 is surrounded by six cyclone separators 25which extend axially therewith and which are equally spaced around thecircumference of the apertures 24. The cyclone separators 25 arecontained within hexagonal tubular boundary walls 26. Each cycloneseparator 25 comprises a frusto-conical side wall 27 (as shown in FIG. 1of the drawings), which tapers inwardly to a cone opening at the lowerend of the body 23.

Referring to FIG. 4 of the drawings, the cyclone separators 25 arearranged in six groups, each group e.g. A (as denoted by the shaded areain FIG. 4) comprises five cyclone separators 25 arranged about arespective aperture 24 and disposed in an arc, which is centred on thecentral axis of the respective aperture 24. It will be appreciated thatone of the six cyclone separators 25 surrounding each aperture 24belongs to an adjacent group of separators.

Five channels 28 extend radially outwardly from the upper end of eachaperture 24 in the upper surface of body 23. The channels 28 leadtangentially into the upper ends of respective cyclone separators 25 ofthe group of separators associated with that aperture.

The lower ends of the frusto-conical walls 27 of the cyclone separators25 terminate above the level of their respective hexagonal tubularboundary walls 26, in order to prevent any cyclonic air flow from beingcarried over to below the bottom surface of the body 23. As shown inFIG. 2, baffles 40 supported by stems 41 extending from the uppersurface of the manifold 21 may be positioned inside each hexagonaltubular boundary wall 26, just below the opening of each cone. Thebottom end of the hexagonal boundary walls 26 open into a gallery 29formed below the body 23 and above the manifold 21. The floor of thegallery 29 comprises an opening at its centre which is connected to theupper end of the elongate tubular container 16 that extends through thecyclone chamber 13 of the first stage 10.

Referring to FIG. 5 of the drawings, an apertured cover plate 30 isfitted to the upper surface of the body 23. The apertures 31 in thecover plate 30 are disposed axially above respective cyclone separators25. The lower surface of the cover plate 30 includes tubular projections32 which extend from the apertures 31 into the upper ends of the cycloneseparators to form so-called vortex finders.

A filter housing 33 is disposed above the second stage 11 and, in use, avacuum is applied to the filter housing 33 to cause an airflow throughthe first and second stages 10, 11 from the dirty air inlet 15. Thetangential orientation of the inlet 15 with respect to the wall 12creates a cyclonic air flow inside the chamber 13 of the first stage 10,whereby air spirals downwardly around the chamber 13 towards its lowerend. As the air flows downwards, the volume of air in the spiral flow isconstantly being diminished by virtue of it having been drawn radiallythrough the perforated shroud 20 towards the second stage 11.

As the air swirls inside the chamber 13, larger (denser) particles inthe rotating airflow have too much inertia to follow the tight curve ofthe airflow and strike the outside wall 12 of the chamber, moving thento the bottom of the cyclone where they are deposited in the lowerregion of the chamber 13.

The air flowing through the perforated shroud 20 is divided equally intosix separate parallel paths along the respective tubular projections 22of the manifold 21. The six separate air flows then divide below thelower surface of the cover plate 30 into five further air flows alongthe respective channels 28. The channels 28 direct the airflowstangentially into the upper end of respective cyclone separators 25 tocreate a cyclonic airflow therein. The airflows spiral downwardly aroundthe frusto-conical walls 27 of the separators 25 towards their lowerends. As the air flows downwards, the volume of air in the spiral flowis constantly being diminished, by virtue it having been drawn radiallyinwardly and axially upwardly through the vortex finders 32.

Any light particles of dust remaining in the airflow from the firststage 10 have too much inertia to follow the very tight curve of theairflow and strike the frusto-conical walls 27 of the separators 25, thedust being carried downwardly through the cone openings and into thegallery 29. The fine dust then falls into the elongate tubular container16. It will be appreciated that the dust separated by both the first andsecond stages 10, 11 can be emptied by removing the closure 14.

A vacuum cleaner in accordance with the present invention is relativelysimple in construction, yet has a substantially improved separationefficiency by enabling large numbers of high-efficiency cyclones to becompactly accommodated.

While the preferred embodiment of the invention has been shown anddescribed, it will be understood by those skilled in the art thatchanges of modifications may be made thereto without departing from thetrue spirit and scope of the invention.

1. A cyclonic separation apparatus comprising: a first separation stage;and a second separation stage connected to said apparatus downstream ofsaid first separation stage, said first separation stage comprising afirst cyclone separator, said second separation stage comprising aplurality of groups of cyclone separators, each group comprising arespective inlet and a plurality of second cyclone separators connectedin parallel with one another to said respective inlet, said apparatusfurther comprising a receptacle for collecting material separated bysaid second cyclone separators, said first and second separation stagesarranged in fluid communication by a plurality of transfer ducts whichare arranged in parallel and which transfer fluid that has been partlycleaned by said first separation stage to the respective inlets of saidgroups of second cyclone separators of said second separation stage,wherein said plurality of transfer ducts extend through the receptacle.2. A cyclonic separation apparatus as claimed in claim 1, wherein saidcyclone separators of said first and second separation stages each havea rotational axis, and said transfer ducts extend substantially parallelto the rotational axis of each of said cyclone separators of said firstand second separation stages.
 3. A cyclonic separation apparatus asclaimed in claim 1, wherein each transfer duct has a downstream end, andthe second cyclone separators of each group are arranged equidistantlyfrom the downstream end of the corresponding transfer duct.
 4. Acyclonic separation apparatus as claimed in claim 1, wherein saidreceptacle is disposed partly above said first separation stage.
 5. Acyclonic separation apparatus as claimed in claim 4, wherein saidreceptacle is disposed partially axially within the first separationstage.
 6. A cyclonic separation apparatus as claimed in claim 1, whereinsaid receptacle is funnel shaped.
 7. A cyclonic separation apparatuscomprising: a first separation stage comprising an upstream cycloneseparator having a longitudinal axis and an outlet; a body disposedaxially of said upstream cyclone separator; and a second separationstage comprising a plurality of downstream cyclone separators arrangedside-by-side relative to one another in said body axially of saidupstream cyclone separator, the downstream cyclone separators beingarranged in a plurality of groups, each of said plurality of groupshaving a respective inlet; and a receptacle for collecting materialseparated by said groups of downstream cyclone separators, saidreceptacle being disposed between the first and second separationstages, wherein said first and second separation stages are arranged influid communication by a plurality of inlet transfer ducts, each inlettransfer duct having an upstream end and a downstream end and extendingfluidly in parallel through the body from said outlet of said upstreamcyclone separator to the respective inlet of the corresponding group ofdownstream cyclone separators, and wherein said plurality of transferducts extend through the receptacle to transfer fluid that has beenpartly cleaned by said first separation stage to the respective inletsof said groups of cyclone separators of said second separation stage.